1. Field of the Invention
This invention relates generally to a laser system controller for controlling the operating parameters of a laser and, more particularly, to a laser system controller for controlling the operating parameters of a solid state diode laser, including ramping of the power output of the laser beam.
2. Discussion of the Related Art
High-power, solid state lasers, such as diode slab lasers, that are used for many purposes, such as cutting, drilling and welding of various materials for precision laser machining (PLM), electronics manufacture, medical treatment, nuclear fusion, laser weapons, etc., are known in the art. A solid state slab laser will include one or more gain modules each having a solid state laser gain medium, such as a crystal of neodymium yttrium aluminum garnet (Nd:YAG), Yb:YAG, Ti:Sapphire or neodymium glass (Nd:Glass), and an optical pumping source to produce a population inversion in the gain medium. The gain medium typically has a slab configuration with a rectangular cross-section and optically polished major side and end faces. The optical pumping source generally is one or more diode arrays positioned adjacent to the side faces of the slab. The laser gain medium absorbs light radiation from the diode arrays to create a population inversion within the medium to produce a laser beam output. The end faces of the slab are preferably formed at a non-perpendicular angle to the side faces so that light travels longitudinally in a zig-zag pattern through the laser gain medium as it is reflected off of the side faces. A high power solid state slab laser of this type is disclosed in U.S. Pat. No. 5,555,254 issued to Injeyan et al., Sep. 10, 1996 and U.S. patent application Ser. No. 08/683,585, filed Jul. 15, 1996, now U.S. Pat. No. 5,790,575, titled Diode Laser Pumped Solid State Laser Gain Module, and assigned to the assignee of the instant invention.
The diode arrays are switched on and off or pumped in a controlled manner to generate a pulsed laser beam emitted from the gain medium that has a particular pulse rate and pulse width. The light output of the diode arrays can be accurately tuned to the absorption line of the active material of the laser gain medium to achieve a high pumping efficiency. An increase in the pulse rate and/or pulse width increases the power output of the laser beam. The diode arrays are fired in a controlled manner to set the pulse width and pulse rate of the output beam. The firing of the various diode arrays for multiple gain modules can be controlled independently of each other or sequenced to further control the overall pulse width and rate of the laser beam, or generate a continuous wave (CW) beam. Therefore, depending on the particular application, the pulse rate and pulse width of the beam output is controlled for efficient laser operation for that application.
Depending on the particular application of the laser beam, it may be desirable to modulate the laser beam to provide high peak power pulses for cutting and drilling applications. The modulator modulates the relatively long pulses from the gain modules to provide short duration beam pulses (such as on the order of 100 nanoseconds) having a relatively high peak power, for example, on the order of 500 kilowatts, that provides greater precision and control for certain applications. In one example, the laser beam pulses generated by the high power solid state laser gain module are modulated by an acoustical optical (AO) modulator that provides the modulation wave for modulating the beam pulses from the gain module. The modulated wave is also capable of being varied in frequency and pulse width to give even greater variability for different applications and materials. U.S. patent application Ser. No. 08/593,961, filed Jan. 30, 1996, titled "Laser Pulse Profile Control By Modulating Relaxation Oscillations", assigned to the Assignee of this application, provides a more detailed discussion of a modulator for a solid state diode slab laser.
To perform a PLM operation, a laser operator will calibrate or program a controller that controls the laser to operate the laser beam at a desired power level and machining sequence to perform the desired machining operation. A single machining operation may include various degrees of cutting, welding and drilling of a single workpiece or multiple workpieces. For example, the machining operation may require a welding operation and then immediately thereafter, drilling of a series of holes and/or cutting the workpiece. The welding operation generally requires different power levels than cutting and drilling operations, and cutting and drilling operations generally require that the beam be polarized and modulated to provide high peak power for efficient operation. Additionally, the welding process itself may require different laser power levels. For example, welding around a corner of the workpiece may require a decrease in power because the welding operation may have to be slowed down and the resulting higher power may damage or burn the material of the workpiece at the slower speed. Further, the laser can be calibrated to weld a certain material, such as steel. If the operator then changes to a different material, such as a different steel, aluminum, copper, etc., different laser settings and output parameters would be required, so the controller needs to be able to be readily changed to the appropriate settings. Thus, the laser controller needs to be programmed to provide these changes in power output level for different operations during the machining operation.
State of the art solid state diode lasers also allow the laser controller to vary the current applied to the diode arrays to change the intensity of the laser beam output. As the sophistication of precision laser machining increases, the sophistication of the controllers also need to increase. The known controllers for solid state diode lasers typically can only change the output power of the laser from one power level to another. It has been recognized that the effectiveness of the laser machining process could be increased by providing a controller that causes the output of the diode arrays to ramp the power of the laser beam from one level to another during the machining operation. Other improvements can be made to the laser controller to increase the efficiency of the laser machining process.
It is an object of the present invention to provide a laser controller that provides for ramping the power output of the laser beam in a solid state diode laser, as well as providing other improvements over the known laser controllers to increase user interface and the like.